Medicare Advantage, Medicaid, and ACA Insurers Deny 12%–18% of Prior Authorization Requests, KFF Finds

A new KFF analysis reveals that in 2025, Medicare Advantage insurers denied 12% of standard prior authorization requests, while Medicaid managed care plans denied 14% and ACA Marketplace insurers denied 18%.

The study examined 14 insurers across the three markets, covering roughly 71 million enrollees. It follows a 2024 CMS final rule requiring payers to publicly post prior authorization metrics such as approval and denial rates, though the data does not indicate which services are most frequently denied.

Across all markets, the median response time for standard requests was about one day. For expedited requests, Medicare Advantage plans responded in a median of half a day, while Medicaid and ACA Marketplace plans took approximately one day. Denial rates for expedited requests were modestly lower than for standard requests.

Denial rates varied significantly by insurer. Among Medicare Advantage plans, standard denial rates ranged from 5% at Elevance to 17% at UnitedHealth Group. In Medicaid managed care, the span was 2% at L.A. Care Health Plan to 23% at Independence Health Group. ACA Marketplace insurers ranged from 3% at GuideWell to 25% at Centene.

Prior authorization denials are seldom appealed, but when they are, many are reversed. About 67% of denials were overturned on appeal in Medicare Advantage, compared with 47% in Medicaid managed care and 43% in ACA federally facilitated Marketplace plans.

Despite increased transparency, significant gaps remain for consumers, KFF notes. Insurers are not required to publish the data in a standardized format, making cross-plan comparisons difficult. “Although a target audience of prior authorization reporting is consumers, those who do not have a deep understanding of health insurance terminology and concepts may struggle to interpret these reports. … Difficulty locating metrics on insurer websites, an absence of more detailed data, and unclear reporting standards could additionally pose challenges for consumers wishing to use the data directly to compare health insurers, as envisioned in the 2024 regulation. However, intermediaries may aggregate and explain the data to make it more accessible for consumers,” KFF said.

Last year, insurers pledged to streamline prior authorization by improving transparency and standardizing electronic submissions. Providers remain skeptical these commitments will yield meaningful improvements.

Photo: Piotrekswat, Getty Images

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